This invention relates to a cassette adapter for a signal playback apparatus. More particularly, the present invention relates to such an apparatus which is suitable for application wherein a compact disc player is connected to an audio cassette tape recorder which is mounted, for example, in a car.
A known construction wherein a cassette adapter, in the form of cassette, is inserted in a cassette insertion port of an audio cassette tape recorder, is disclosed in U.S. Pat. No. 4,734,897. A cable terminal extending from the cassette adapter is connected to an audio output terminal of, for example, a portable compact disc player, thereby supplying an audio signal produced by the compact disc player to the audio cassette tape recorder.
The cassette adapter is provided with an impedance conversion circuit for adjusting the impedance level of the audio signal outputted from the compact disc player and which is fed to a magnetic head on the cassette tape recorder side. Thus the audio signal reproduced by the compact disc player can be heard by means of a cassette tape recorder mounted on the car side.
As is well known, automotive vehicles are usually provided with a so-called ACC power-terminal which is interconnected with an engine ignition switch to control the supply of voltage.
In this prior art arrangement, electric power (e.g. 12 volts) is supplied to the audio cassette tape recorder from the ACC power source, and therefore is controlled in an on/off manner depending on the position of the ignition key.
On the other hand, the compact disc player is provided with its own battery, for example, of the re-chargeable type.
Thus, power is supplied to the compact disc player even in the case wherein the ACC power is cut-off to the cassette tape recorder by the manipulation of the ignition key and the associated opening of the engine ignition switch.
Consequently, there is a problem that a battery of the compact disc player becomes completely discharged if the compact disc player is left switched on for a long time.